Strength and Durability Characteristics of Concrete Incorporating a Pelletized Blast Furnace Slag


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Title: Strength and Durability Characteristics of Concrete Incorporating a Pelletized Blast Furnace Slag

Author(s): V.M. Malhotra

Publication: Special Publication

Volume: 79


Appears on pages(s): 891-922

Keywords: air entraining agents; blast strength; concrete durability; flexural durability; pellets; plasticizers. furnace slag; compressive -- strength; freeze-thaw

Date: 5/1/1983

This report gives results of laboratory investigations to determine the strength and freeze-thaw durability characteritics of concrete incorporating pelletized iron blast furnace slag from a Canadian source. A series of thirty-two 0.062-m3 mixes was made with water to cement plus slag ratios ranging from 0.30 to 0.65, and the percentage of slag used as a partial replacement for normal portland cement ranged from 25 to 65% by weight. All mixes were air entrained and some incorporated a superplasticizer in addition to an air-entraining agent. A number of 102 x 203-mm cylinders were cast for testing in compression and splitting ten-sion at ages up to one year. Test prisms, 89 x 102 x 406 mm, were also cast to determine flexural strength and freeze-thaw durabil-ity. Regardlessofthe water to cement plus slag ratio the strength of control concrete was generally higher than that incorporating slag. The difference in strength narrows between 7 and 91 days depending on the water to cement pIus slag ratio; beyond 91 days, the difference widens again. The above strength development pat-tern is more marked for concrete with water to cement plus slag ratios of 0.30 and 0.38. The last day flexural strength of concrete ranged from 4.2 to 6.0 MPa for a water-to-cement plus slag ratio of 0.56. The flex-ural strength of concrete with water-to-cement plus slag ratios of 0.46 and 0.56 is comparable to or greater than the corresponding strength of control concrete. The reverse is true for concrete with a water-to-cement-plus-slag ratio of 0.38 for both air en-trained, and air entrained and superplasticized concretes; at 65% slag replacement, there is a drop in strength in the order of 20% compared with the control concrete. Durability studies indicated that regardless of the water to cement plus slag ratio and whether the concrete was air entrained or air entrained and superplasticized, the test prisms performed satisfactorily in freeze-thaw tests (ASTM C666 Procedure B) with minor exceptions.